Disconnector for surge arresters

ABSTRACT

A disconnector is attached to and electrically in series with a surge arrester. The disconnector has a breakable shell that is broken by explosion of a cartridge within the shell when excessive current flows across an arcing gap. The disconnector has a top electrode and a bottom electrode with the top electrode connected to the surge arrester and the bottom electrode connectable to a connector wire. An annular electrically conductive elastomer gasket is compressed between the upper and lower electrode to provide a high resistance current path around the arcing gap and also to seal the cartridge from the outside atmosphere.

United States Patent 1191 Marek et al.

541 DISCONNECTOR FOR SURGE ARRESTERS v [75] lnventors: James R. Marek, South Milwaukee; Stanley S. Kershaw, Jr., Greendale,

1 UNITED STATES PATENTS 2,548,112 4/1971 Kaminky ..337/30 [451 Jan. 9, 1973 3,100,246 8/1963 Riley ..3l7/66 X Primary Examiner-James D. Trammell Attorney--R. J. Falkowski [57] ABSTRACT A disconnector is attached to and electrically in series with a surge arrester. The disconnector has a breakable shell that is broken by explosion of a cartridge within the shell when excessive current flows across an arcing gap. The disconnector has a top electrode and a bottom electrode with the top electrode connected to the surge arrester and the bottom electrode connectable to a connector wire. An annular electrically conductive elastomer gasket is compressed between the upper and lower electrode to provide a high resistance current path around the arcing gap and also to seal the cartridge from the outside atmosphere.

14 Claims, 2 Drawing Figures DISCONNECTOR FOR SURGE ARRESTERS This invention relates to disconnectors for surge arresters, particularly to disconnectors having a high resistance bridging the arcing gap of the disconnector.

As described in U.S. Pat. No. 2,551,858, Stoelting et al., Resistor Type of Isolator for Lightning Arresters, it is advantageous to provide a resistor connected in parallel with the gap of a disconnector to provide a current bypass path for preventing the building up of potential difference between the upper and lower electrodes of the disconnector. A potential difference is undesirable because it can produce low current arcing to ground across the gap, thereby creating a corona that produces radio interference.

With prior art resistor type disconnectors, however, it is difficult to provide a disconnector that is easily as sembled and at the same time is substantially moistureproof. With this invention a simple construction utilizes an elastomer material with a desirable electrical resistance as a gasket between the upper and lower electrodes. The gasket serves a dual function by providing a high resistance current path around the arcing gap and providing an effective seal for the chamber in which the blank cartridge is retained.

The objects and advantages of this invention will be apparent from the following detailed description.

FIG. 1 is a side view of a typical surge arrester having a disconnector according to this invention attached; and

FIG. 2 is a cross-sectional side view of the disconnector shown in FIG. 1.

Referring to FIG. 1, a lightning or surge arrester comprises a ceramic insulating casing 11 of any type known in the art, an upper insulating cover 12 covering an electrode contact (not shown) connected to a connecting conductor 13, and a disconnector or isolator l4 electrically and mechanically connected to the bottom of the surge arrester. The surge arrester is of any type known in the art, generally called distribution arresters, that provides the appropriate protection against transient overvoltages by typically utilizing valve blocks and spark gaps to protect the electrical system into which it is connected.

Disconnector 14, as shown in FIG. 1, is connected onto ceramic casing 1 1 by a dished flange portion or arrester cap 15A of an upper electrode 15 pressed or spun around a lower ridge 17 of ceramic casing 11. Disconnector 14 comprises upper electrode 15, a center breakable insulating housing 18, and a lower electrode assembly 16. Upper electrode 15 is typically electrically connected to the valve block and spark gap assembly of the surge arrester by an electrically conducting spring (not shown) that is compressed between the bottom of the valve block and spark gap assembly and the upper electrode and conducts current from the valve block and spark gap assembly to the disconnector.

Referring to FIG. 2, center housing 18 is made of any suitable insulating material, such as bakelite, that will suitably-break upon the explosion of a cartridge within the housing. The center housing has an opening 22 extending therethrough thathas an upper threaded portion 22A and a lower portion 22C of-smaller diameter that forms a shoulder 228 between the upper and lower portion.

Upper electrode 15 comprises flange portion 15A which is adapted to be pressed around lower ridge 17 of ceramic casing 11, a group of water drain holes 20 for permitting drainage of water from the dished portion, and a threaded conducting extension 21 attached to flange portion 15A in any known manner, as by brazing. Electrode 15 connects to center housing 18 by being screwed into threaded portion 22A of opening 22 of center housing 18.

Lower electrode assembly 16 comprises a lower conductive electrode 19, a nut 23, a nut 24, a threaded shaft 25 for receiving nuts 23 and 24, a wire retaining clamp 26, a seating flange 27 arranged to engage shoulder 22B of opening 22 in center housing 18 so that the tightening of nut 23 retains lower electrode 19 in center housing 18, an upper cylindrical extension 31, a recess 30 in the upper portion of extension 31, and a blank cartridge 29 adjacent the surface of extension 31 within recess 30. Lower electrode 19 is inserted into center housing 18 through threaded portion 22A of opening 22 to rest flange 27 upon shoulder 22B, is retained in position by tightening of nut 23, and is connected to an appropriate connecting wire (not shown) by tightening nut 24 to close clamp 26 around a connecting wire.

An annular elastomer gasket 32 fits between flange 27 of lower electrode 19 and an annular lip 33 formed by a countersunk conical recess 34 in conducting extension 21 of upper electrode 15 and is compressed between flange 27 and lip 33 upon the screwing in of upper electrode 15 into the center housing. Conical recess 34 and cylindrical extension 31 are spaced apart to provide an arcing chamber between them.

In the operation of the lightning arrester the disconnector functions in a manner known in the art so that any buildup of charge is drained through elastomer gasket 32 from upper electrode 15 through annular lip 33 to lower electrode 19 to ground through the connecting wire. Upon any low level arcing, arcing typically occurs in the arcing chamber between arcing surfaces formed by conical opening 34 of threaded extension 21 and the circular edge of extension 31 of lower electrode 19. When the arcing has occurred for a sufficient period of time or is intense enough, the temperature of blank cartridge 29 is raised sufficiently to burn the cartridge, and the disconnector housing is broken by the breaking of center housing 18 to separate the electrodes and open the electrical circuit to ground. In this manner, when the surge arrester is damaged so that excessive current flows through disconnector 14, the

disconnector operates to electrically remove the surge arrester from the system.

Gasket 32 may be of any sealing material that has electrical conducting properties within the ranges desired. Typically the type of materials known as conductive elastomers has the desirable characteristics, and the resistance is typically selected to be in the range of to 1000 ohms, but resistances beyond this range could be used for some applications. The use of the conductive elastomer gasket between the upper and lower electrodes of the disconnector provides a simple, effective resistance discharge path and at the same time prevents moisture from entering along either the bottom or the top of the disconnector to the cartridge. Such accumulation of moisture could destroy the capability of the cartridge to fire under arcing conditions. This is particularly necessary because the period of installation of a disconnector extends over 'many years, and reliable operating characteristics over this period are essential. The gasket specifically prevents moisture from leaking into the chamber along the threads between center housing opening 22 and threaded extension 21 of upper electrode and along threaded shaft 25 of lower electrode 19. Thus, the

chamber withthe arcing surfaces between conical recess 34 and blank cartridge 29 is completely and easily sealed from the outer atmosphere.

We claim:

1. A disconnector for surge arresters comprising! a breakable insulating housing having an opening;

upper and lower electrically conductive electrodes connected to the housing and having respective arcing surfaces spaced apart from each other to form an arcing chamber at least in part within the opening;

a cartridge adjacent to one of the arcing surfaces adapted to explode when current through the disconnector exceeds a preselected level to thereby break the housing and separate the electrodes; and

' an electrically conductive elastomer gasket having a selected electrical resistance compressed between the upper and lower electrode to thereby seal the arcing chamber and cartridge from the atmosphere and provide a high resistance current path between said electrodes.

- 2. A- disconnector according to claim 1 wherein said elastomer gasket is an annular gasket.

3. A disconnector according to claim 1 wherein said electrodes are within the opening.

4. A disconnector according to claim 3 wherein said housing opening has a threaded portion and said upper electrode has a threaded extension adapted to be screwed into said threaded portion.

5. An electrical disconnector for connection to a surge arrester in an electrical circuit comprising:

a breakable insulating. housing having an opening therethrough;

a first and a second electrical connecting electrode retained adjacent at least part of said opening and each having respective arcing surfaces spaced apart from each other;

an electrically conductive elastomer gasket having a selected electrical resistance compressed between the arcing surfaces of the upper and lower electrodes to form a sealed chamber with said electrodes; and

a cartridge adjacent said chamber adapted to explode when current through the disconnector exceeds apreselected level to thereby break the housing and open the electrical circuit.

6. A disconnector according to claim 5 wherein said breakable insulating housing opening has an upper portion and a lower portion of smaller diameter with a shoulder at the top of said lower portion and said second conducting electrode is adapted to pass through the'lower opening of the insulating housing and has a flange near the upper end thereof adapted to seat upon the insulating housing shoulder.

7. A disconnector according to claim 6 wherein said breakable insulating housing opening has an upper threaded portion and said first conducting electrode has a threaded extension adapted to be screwed into said upper threaded portion.

8. A disconnector according to claim 7 wherein said extension is recessed at its lower end to form at least part of the chamber around an annular lip.

9. A disconnector according to claim 8 wherein said second conducting electrode has a recess adapted to receive the cartridge and wherein said cartridge is in said recess.

10. A disconnector according to claim 9 wherein said conductive elastomer gasket'is annular and is compressed between the annular lip and the lower electrode flange.

11. A disconnector according to claim 10 wherein said second electrode has a cylindrical extension above end and said first electrode has a threaded extension adapted to screw into said threaded portion and is adapted to be electrically connected into the, electrical circuit.

l4. An electrical disconnector according to claim 5". I

wherein said elastomer gasket. is annular to form the sealed chamber within the gasket. 

1. A disconnector for surge arresters comprising: a breakable insulating housing having an opening; upper and lower electrically conductive electrodes connected to the housing and having respective arcing surfaces spaced apart from each other to form an arcing chamber at least in part within the opening; a cartridge adjacent to one of the arcing surfaces adapted to explode when current through the disconnector exceeds a preselected level to thereby break the housing and separate the electrodes; and an electrically conductive elastomer gasket having a selected electrical resistance compressed between the upper and lower electrode to thereby seal the arcing chamber and cartridge from the atmosphere and provide a high resistance current path between said electrodes.
 2. A disconnector according to claim 1 wherein said elastomer gasket is an annular gasket.
 3. A disconnector according to claim 1 wherein said electrodes are within the opening.
 4. A disconnector according to claim 3 wherein said housing opening has a threaded portion and said upper electrode has a threaded extension adapted to be screwed into said threaded portion.
 5. An electrical disconnector for connection to a surge arrester in an electrical circuit comprising: a breakable insulating housing having an opening therethrough; a first and a second electrical connecting electrode retained adjacent at least part of said opening and each having respective arcing surfaces spaced apart from each other; an electrically conductive elastomer gasket having a selected electrical resistance compressed between the arcing surfaces of the upper and lower electrodes to form a sealed chamber with said electrodes; and a cartridge adjacent said chamber adapted to explode when current through the disconnector exceeds a preselected level to thereby break the housing and open the electrical circuit.
 6. A disconnector according to claim 5 wherein said breakable insulating housing opening has an upper portion and a lower portion of smaller diameter with a shoulder at the top of said lower portion and said second conducting electrode is adapted to pass through the lower opening of the insulating housing and has a flange near the upper end thereof adapted to seat upon the insulating housing shoulder.
 7. A disconnector according to claim 6 wherein said breakable insulating housing opening has an upper threaded portion and said first conducting electrode has a threaded extension adapted to be screwed into said upper threaded portion.
 8. A disconnector according to claim 7 wherein said extension is recessed at its lower end to form at least part of the chamber around an annular lip.
 9. A disconnector according to claim 8 wherein said second conducting electrode has a recess adapted to receive the cartridge and wherein said cartridge is in said recess.
 10. A disconnector according to claim 9 wherein said conductive elastomer gasket is annular and is compressed between the annular lip and the lower electrode flange.
 11. A disconnector according to claim 10 wherein said second electrode has a cylindrical extension above the flange, said elastomer gasket surrounds said cylindrical extension, and said recess is at the upper end of said cylindrical extension.
 12. An electrical disconnector according to claim 5 wherein said first electrode extends through one end of the opening and the second electrode extends through the other end.
 13. An electrical disconnector according to claim 12 wherein said opening in the housing is threaded at one end and said first elEctrode has a threaded extension adapted to screw into said threaded portion and is adapted to be electrically connected into the electrical circuit.
 14. An electrical disconnector according to claim 5 wherein said elastomer gasket is annular to form the sealed chamber within the gasket. 